In fiber optic gyroscopes (FOGs), rotation rate information is encoded in the optical phase shift between two waves counter-propagating through a fiber coil. The waves are then made to impinge together on a photodetector, where the rotation-induced phase determines the optical interference intensity and the resulting photocurrent. This electric current is then typically transimpedance-amplified into a voltage for signal processing, possibly with additional analog or digital gain applied. In high-performance FOGs, the voltage signal is generally amplified with as much gain as possible to maximize the ratio of rotation signal to noise.
Certain electronic components used in the signal processing path of the gyroscope can impose limits on the maximum usable gain. For example, many high-performance FOGs use an analog-to-digital converter (ADC) to digitize the photodetector signal. These ADCs often have rather narrow damage thresholds, limiting the safe input voltage range to, for example, 0V-5V. This limited safe input voltage range reduces the maximum gain that can be applied in the electronics chain leading up to the ADC.
Circuits currently available to clamp voltages to a safe input voltage range significantly distort the input voltage waveform and moreover permit large gyroscope transient events to end up in the acquisition region of the rate gyroscope circuit. Such distortion increases noise, bias modulation pick-up, scale factor nonlinearity, and other factors, which deteriorate the gyroscope performance.